swiftc dump ast without any swiftc logging

[max-leuthaeuser]

Using the -dump-ast -dump-ast-format json flags logs all stdout/stderr from the compiler.

E.g.,

/usr/bin/swiftc -module-name SwiftHelloWorld <other-args-omitted> -dump-ast -dump-ast-format json

may result in:

{ // full json omitted }
error messages
...
 #7 0x00007ff68b556ebe (.../Swift/Toolchains/6.1.2+Asserts/usr/bin/swift-frontend.exe+0x2046ebe)
...

warning messages
{ // another full json omitted }{ // another full json omitted }
...

Is there any swiftc flag to clean the output and actually only receive the json strings if any?
Piping the output (1>, 2>) does not help as many log messages are still intertwined with the actual json output.

[bnbarham]

As far as I can see, -dump-ast goes to stdout and diagnostics + crash stack traces go to stderr:

> swiftc -dump-ast -dump-ast-format json t.swift > temp
t.swift:6:3: warning: result of call to 'foo()' is unused [#no-usage]
4 |
5 | func bar() {
6 |   foo()
  |   `- warning: result of call to 'foo()' is unused [#no-usage]
7 | }
8 |

> > DEVELOPER_DIR=/Applications/xcodes/dev/Xcode17A.app xcrun swiftc -dump-ast -dump-ast-format json t.swift 2> temp
{... json output only ...}

Piping the output (1>, 2>) does not help as many log messages are still intertwined with the actual json output.

Could you give a concrete example here?

[max-leuthaeuser]

It works nicely for single files, yes.
But let's try a module containing multiple files instead. If any of these files result in an compilation error the jsons created up to this point are printed to stderr together with the message for the faulty file.

You can observe this e.g., on https://github.com/migueldeicaza/SwiftGodot and it's Sources/SwiftGodot module.
Built it with "swift build --verbose > build.txt".
Replay the call to .../swiftc -module-name Swiftgodot with the dump options appended. (Remove -emit... etc.)

[bnbarham]

Ah I see, thanks:

> swiftc -dump-ast -dump-ast-format json t.swift t2.swift 2> temp
# no output (everything is stderr)

[max-leuthaeuser]

Exactly!
Sorry for the unclear initial issue description as I was unable to provide a minimal reproducing example.

At a first glance at the "dump ast as Json" releated PRs I was unable to spot the code responsible for the error and out stream creation handling. But I am sure that should be fixable.
Who is the right person to assign for this issue?